Treatment of porous article

A method for modifying at least one property of an at least partially sintered expanded polytetrafluoroethylene (ePTFE) membrane wherein the property is selected from the group of oleophobicity, hydrophilicity, electrical conductivity, ion conductivity and color, said method comprising the steps of:

• providing an at least partially sintered ePTFE membrane having interconnecting pores extending through the membrane;
• providing a treatment material;
• dissolving the treatment material in a fluid at supercritical conditions;
• exposing the ePTFE membrane to the dissolved treatment material and fluid at supercritical conditions for a predetermined amount of time at a predetermined temperature and pressure and causing said ePTFE membrane to swell;
• moving a portion of said treatment material into said swelled ePTFE membrane material;
• causing at least one property of the ePTFE membrane to be modified while the membrane is exposed to the dissolved treatment material and supercritical fluid;
• changing the condition of the fluid to cause the treatment material precipitate onto surfaces of the ePTFE membrane defining the pores in the ePTFE membrane and thereby effect the modification of the property of the ePTFE membrane;
• and
• permitting said ePTFE membrane to return to its original size and configuration during said changing step to absorb a portion of said treatment material;
• wherein a portion of the treatment material absorbed into the ePTFE membrane thereafter exudes from said ePTFE membrane.

A method for treating an at least partially sintered expanded polytetrafluoroethylene (ePTFE) membrane having an amorphous portion and a crystalline portion, said method comprising the steps of:

• providing an at least partially sintered microporous ePTFE membrane having surfaces defining pores;
• exposing the ePTFE membrane to a coating treatment material in a fluid under supercritical conditions to swell a portion of the ePTFE membrane from an initial size;
• breaking bonds in the crystalline portion of the ePTFE membrane by the swelling to render the swelled portion more amorphous;
• and
• removing the fluid at supercritical conditions from the ePTFE membrane so the swelled portion of the ePTFE membrane returns towards the initial size and the crystalline bonds remain broken in that portion of the ePTFE membrane;
• and causing said treatment material to precipitate onto the surfaces defining said pores of said membrane;
• and causing said ePTFE membrane material to absorb a portion of said treatment material.

A method for modifying at least one property of an at least partially sintered expanded polytetrafluoroethylene (ePTFE) porous membrane, said method comprising the steps of:

• providing an at least partially sintered expanded polytetrafluoroethylene (ePTFE) membrane having interconnecting pores of an average pore size no greater than 10 micron extending through the membrane;
• providing a treatment material;
• dissolving the treatment material in a fluid having a surface tension less than 5.0 dynes/cm;
• modifying at least one property of the membrane while the membrane is exposed to the dissolved treatment material and fluid;
• and wherein said modifying step comprises moving portion of the treatment material into a swelled portion of the membrane material;
• and changing the condition of the fluid in such a manner that the membrane retains the modified property;
• and
• permitting said membrane to return towards its original size and configuration to absorb a portion of said treatment material, wherein a portion of said absorbed treatment material thereafter exudes from said membrane.